Save site as Templete using PowerShell

You can create site template using SharePoint site setting UI. alternatively you could PowerShell

$Web=Get-SPWeb http://sp2013.com/sites/template
$Web.SaveAsTemplate("Template Name","Template Title","Template Description",1)

If you want to save specified site as template along with data use 1, otherwise use 0 in forth parameter of SaveAsTemplate().

After running above commands, the newly created template will be available in site collection "Solutions" gallery.